/*
 * Copyright (c) 2012 Robert Burrell Donkin robertburrelldonkin.name
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this software 
 * and associated documentation files (the "Software"), to deal in the Software without restriction, 
 * including without limitation the rights to use, copy, modify, merge, publish, distribute, 
 * sublicense, and/or sell copies of the Software, and to permit persons to whom the Software 
 * is furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in all copies or 
 * substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING 
 * BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, 
 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 * 
 */
package name.robertburrelldonkin.alfie;

import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.CountDownLatch;

public class Pool<Subject, Result> implements Actor<Subject, Result> {

	private final ActorFactory<Subject, Result> factory;
	private final int size;
	private final BlockingQueue<Actor<Subject, Result>> queue;
	private final CountDownLatch activeActors;
	private boolean open = false;
	
	public Pool(ActorFactory<Subject, Result> factory, int size) {
		super();
		this.factory = factory;
		this.size = size;
		queue = new ArrayBlockingQueue<Actor<Subject, Result>>(size);
		activeActors = new CountDownLatch(size);
	}

	public synchronized Pool<Subject, Result> open() {
		if (!open) {
			for (int i=0;i<size;i++) {
				queue.add(factory.build());
			}
		}
		return this;
	}
	
	public Result act(Subject subject) throws Exception {
		final Actor<Subject, Result> actor = queue.take();
		try {
			return actor.act(subject);	
		} finally {
			queue.put(actor);
		}
	}

	public void finish() {	
		while (activeActors.getCount() > 0) {
			Actor<Subject, Result> actor;
			try {
				actor = queue.take();
				activeActors.countDown();
				actor.finish();
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
		}
	}

}
